Taking my camera to school is risky, so I'd like a bag to keep it in when I'm not using it.

A normal bag would be fine..but I have a backpack on me most of the time, so having an over-the-shoulder bag would be annoying, and would look funny. Another thing is that I'd have to either set it down, or like..tie it to my belt loop or something while shooting (with two hands)

I figured someones opinion about a specific bag would be better than the description of some amazon product.

Shooting with one or 2 bags is not really a problem, I've done it multiple times (also with a one-strap bag).

As for how to carry it: you can just put it in your backpack, it's not too fragile. Don't put too much stress on the plastic lens mount of the 18-55 though. You can always opt to get a top loading zoom mini (TLZ mini) from lowepro for extra protection, whether you use it inside your bag or not

_________________I take pictures so quickly, my highschool was "Continuous High".